1. Field of the Invention
This invention relates to a gases supply and gases humidification apparatus, particularly but not solely for providing respiratory assistance to patients or users who require a supply of humidified gas at positive pressure for the treatment of diseases such as Obstructive Sleep Apnea (OSA), snoring, or Chronic Obstructive Pulmonary Disease (COPD) and the like. In particular, this invention relates to a gases supply apparatus which has an integral humidifier chamber, so as to form a combined assisted breathing unit and humidifier.
2. Summary of the Prior Art
Devices or systems for providing a humidified gases flow to a patient for therapeutic purposes are well known in the art. Systems for providing therapy of this type, for example CPAP therapy, have a structure where gases at the required pressure are delivered from an assisted breathing unit or blower unit to a humidifier chamber downstream from the blower. As the gases are passed through the heated, humidified air in the humidifier chamber, they become saturated with water vapour. The gases are then delivered to a user or patient downstream from the humidifier, via a gases conduit. Humidified gases can be delivered from a modular system that has been assembled from separate units (that is, a system where the humidifier chamber/heater and the breathing unit/blower are separate items) connected in series via conduits. An example of a system of this type is shown in FIG. 1. However, it is becoming more common for integrated blower/humidifier systems to be used, as shown schematically in FIG. 2. A typical integrated system consists of a main ‘blower’ or assisted breathing unit which provides a pressurised gases flow, and a humidifier unit that mates with or is otherwise rigidly connected to the blower unit. This mating occurs for example by a slide on or push connection, so that the humidifier is held firmly in place on the main blower unit. An example of a system of this type is the Fisher and Paykel Healthcare ‘slide-on’ water chamber system shown and described in U.S. Pat. No. 7,111,624. A variation of this design is a slide-on or clip-on design where the chamber is enclosed inside a portion of the integrated unit in use. An example of this type of design is shown in WO 2004/112873. This specification describes a blower, or flow generator 50, and an associated humidifier 150. The blower unit 50 and the humidifier unit 150 are brought together in use and connected as described in paragraph 00119 of this document. The humidifier chamber, or water tub (698, 699, 700) is described in paragraphs 00132 to 00141. It should be noted that the water tub can either be filled through the passage 722 (described in detail in paragraph 00126), which is located on the rear wall of the humidifier unit 150, or by removing the tub lid 700. The process for removing the lid is described in paragraph 00136. When the lid of the humidifier unit (lid 648) is closed, this pushes the water tub into position.
WO 04/112873 also describes a power supply cavity, shown as item 65 in FIG. 6, and described in paragraphs [0096] and [0097]. The compartment is described as being vented to atmosphere (if necessary) for cooling. FIG. 7 shows the power supply board 124 and the cavity 65. As described in paragraph [00100], air enters the blower through an air inlet 84, communicating with passage 85 above the power supply cavity 65, with the passage then leading to the muffler cavity 134 in which the fan unit 90 sits. It should be noted that as shown in FIG. 6, the power supply cavity 65 is insulated from the air supply passage 85 and the muffler cavity 134 by two walls, with an airgap between them. Using this air flow to cool the power supply board is not discussed in this specification.
A further example of this type of design is shown in U.S. Pat. No. 7,096,864. The humidifier chamber 17 is partly enclosed in a humidifier unit 16, which is push-fitted to a separate blower or CPAP unit 1.
In the devices shown in WO 2004/112873 and U.S. Pat. No. 7,096,864, the blower unit and the humidifier unit are both discrete, ‘table-standing’ units, pushed together to mate pneumatically and electrically.
A further variation of the integrated blower and humidifier type of design is shown in U.S. Pat. No. 6,435,180. A water container or humidifier chamber 66 has a lid 72. The lid 72 of the humidifier chamber 66 is located in use underneath a cover 94 that covers the entire top part of the unit. Cover 94 and lid 72 can be removed simultaneously by a user passing their fingers and thumbs through the holes 92. Two separate air streams (a humidified stream and a dry stream) are mixed in the housing of the device to create one air stream that is provided to a user (Column 6, lines 23-34). It is not intended that any of the elements such as the lids or the chamber are connected together with fasteners or similar, so that the unit can be disassembled easily (column 6, lines 46-55).
A humidifier chamber with a lid is described in U.S. Pat. No. 5,588,423. Lid 11 closes the top of the chamber 2.
The advantage of these types of integrated devices is that generally they are more compact and discrete than a modular breathing circuit that has been assembled from separate units. A compact and discrete unit is particularly advantageous for home use units, where bedside space is limited, and where a user may also have to transport and set up their own personal unit elsewhere, for example if staying overnight away from home. With compact and integrated units, the set up is generally easier for a user. Generally, home units are used for the relief of sleep apnoea. A mid-use point will usually be during the night, during a users sleep cycle. If refilling or similar is required during use, a user will need to wake up to perform this operation. Having been woken up, the user is required to remove the humidifier chamber from the integrated unit, refill it, then return it into position and if necessary reassemble the unit. Humidifier chambers are often sealed units, and cannot be easily opened. That is, they are sealed except for the inlet and outlet ports. Chambers of this type are filled through either the inlet or the outlet port of the chamber. This refilling operation can be time-consuming, difficult to perform at bedside, and can require a level of concentration that a user may find difficult to muster in the middle of the night. It is especially important to minimise disruption to a users sleep pattern if they suffer from sleep apnoea, as the intent of the therapy is to minimise disruption to their sleep patterns, and any additional factors that might disturb them are therefore unwelcome. Although chambers with lids are known in the art as described above, these are generally not designed with the intended purpose that the lid that it can be easily removed during use, for example for refilling the chamber. Humidifier chambers with removable lids are generally not designed in such a manner that simplifies this operation. It is generally intended that the lid will only be removed when the unit is not in use, to access the inner surfaces of the chamber for e.g. cleaning or similar.
Further problems can arise when filling or cleaning these units, as nearly all of the respiratory humidification systems currently available use water as a humidification medium, and cleaning will almost always be carried out with a water based cleaner. Blower and humidifier units are operated and controlled electrically, and problems can occur if the electronic parts, such as external user controls, are not protected. If the controls are not protected, any accidental water spillage that takes place can potentially short-circuit the controls and disrupt the operation of the system.
Control knobs that are designed in such a manner that the opportunities for spillage to cause damage are known in the art.
U.S. Pat. No. 6,812,435 describes a control knob for an oven that is mounted on a continuous horizontal plate, and which can be moved around on the plate. Magnetic actuators under the plate and in the knob interact, with Hall sensors detecting the changes in the magnetic fields. A control unit receives the signals from the Hall sensors and alters the output parameters of the stove accordingly.
US 2005/0205395 describes a control knob arrangement where magnetic elements are embedded in the body of a knob 2, with their magnetic fields interacting as the knob is rotated with e.g. rotary field sensor 25 (a Hall sensor in the embodiment described). The knob sits in a recess 16 in a panel 14, and is held in place on the panel by retaining pegs 11 that pass through an open aperture at the bottom of the recess 16.
As outlined above, it can be difficult to concentrate and carry out complex operations in the middle of the night (or during the middle of a users sleep sequence), or if a users sleep pattern has been disrupted. It is therefore considered important, or at least preferred, that the blower and humidifier controls are as simple and intuitive as possible. Also, that the number of steps necessary to make adjustments or carry out an operation is minimised.
One of the advantages of an integrated unit is that generally they are compact and discrete, and are particularly suited for home use as their ‘footprint’—e.g. on a bedside stand or similar—tends to be less than modular units. It is therefore particularly advantageous if the power supply unit can be built into, or located inside, the housing or external shell of the integrated blower/humidifier, in order to keep the ‘footprint’ of the unit as small as possible. However, if the power supply pack is external—located outside the housing or shell of the ventilator/humidifier unit, the heat can dissipate to atmosphere easily. If the power supply unit is located inside the shell or housing, heat from the power supply unit cannot dissipate as easily. The ventilator or ‘blower’ units that form part of these integrated, compact units draw a considerable amount of power. The power packs or power plants used to provide power to the motor or drive units usually generate a considerable amount of heat as a by-product of this power generation. That is, the power packs and associated circuitry (for example, transformers or similar components) become hot as a consequence of powering the operation of the ventilator/humidifier. As the temperature of the power supply increases, it works less effectively, and more power is drawn to compensate for the drop in efficiency, leading to a greater heat output, and a corresponding further drop in efficiency—a negative feedback loop. It can be seen that it is important to prevent the power supply unit from overheating, or at least from heating up to a temperature that is over the upper limit of an optimum operating range. This can be difficult to achieve if the power supply is enclosed in the external shell of an compact unit that is specifically designed to be as small as possible, with internal free space minimised. This can be especially important if the size of the power supply itself has been minimised, and the airgaps between components have been minimised, potentially leading to further difficulties with heat dissipation.
US 2007/0048159 discloses a blower unit that includes electronic circuitry (referred to generally as electronics seating portion 120). An air inlet 140 is shown directly below this electronic circuitry. It is not clear from the specification whether the electronic circuitry is heat-producing circuitry for example, power circuitry, which generally produces a considerable amount of heat, or if it is control circuitry, which generates much less heat and does not generally require cooling. It is also unclear from the specification how the structure between the air path and the electronic circuitry is configured. The wall between the components and the air flow could potentially be thick enough to insulate the electronic circuitry from any cooling effect produced by the air flow.
Users of domestic breathing assistance apparatus (such as a CRAP device) may occasionally wish to travel and spend the night (or longer) away from home. It is normal for the breathing assistance apparatus to be carried in some form of bag or carry case. Many users prefer to have the option of carrying their device as hand luggage e.g. if flying, so that they are assured of arriving at their destination with the device. This necessitates a compact carry case (as well as a compact device). Rigid or hard carry cases are known, which allow the user a convenient safe method to travel with their device. One of the problems with any type of carry case is that when the device is placed inside is the user forgetting to empty the water from the humidification chamber. Spillages of water from the chamber can occur if the unit is packed and carried without the contents of the chamber being emptied.
It is an object of the present invention to provide a breathing assistance apparatus which goes some way to overcoming the abovementioned disadvantages or which at least provides the public or industry with a useful choice.